The present invention relates generally to a method and system for data display and input through a display monitor screen. More specifically, the invention relates to a system and method for displaying graphic or handwritten images which precisely correspond to images drawn on the display monitor screen by a data input apparatus.
Conventionally, the data input apparatus for such graphic image display systems comprises a tablet, a mouse, and the like. On the other hand, the display monitor for the graphic image display system is usually a cathode-ray-tube (CRT) display. Usually, the combination of a CRT display and a touch tablet is used. In this case, the touch tablet may be located away from the display monitor screen, or may alternatively be placed on the display monitor screen. In either case, data input is performed by means of a tablet pen.
In the former case, some problems are encountered in entering data through the touch tablet. For instance, it is rather cumbersome to input data through a touch tablet separated from the display monitor screen on which input data are reproduced as graphic images. In the latter case, the problems encountered in the former case do not arise since the touch tablet and the display monitor screen are at essentially the same position. However, in this case, due to parallax error caused by the curvature and thickness of the screen glass of the CRT display, deviations between the writing position and display position tend to occur. Furthermore the parallax error varies with errors in gun deflection in the CRT display and the eye position of the operator. In addition, the display position varies with contrast, brightness and/or terrestrial magnetism. Furthermore, in order to input data through a touch tablet mounted on the display monitor screen, the operator tends to move closer to the display screen which tends to add to eye strain. An additional defect in the conventional graphic image display system is the relatively low resolution of the CRT monitor.